Bone mill

ABSTRACT

A bone mill for converting cadaver bone into controlled size fragments. Bone is fed into a vertical channel which is horizontally intersected by a toothed cutter bar. The cutter bar shearingly contacts the front edge of the bone supply channel shearing the bone into fragments. The cutter bar is driven by an air-cylinder driven by an external source of compressed air. A relay box on the bone mill may be unplugged from the mill and removed allowing the remainder of the mill to be sterilized in an autoclave.

United States Patent [191 Stayton et a1.

[ 1 Dec. 24, 1974 I 1 BONE MILL [75] Inventors: LeRoy M. Stayton; Theodore L.

Herling, both of Ridgecrest, Calif.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

[22] Filed: Sept. 29, 1972 [21] Appl. No.: 293,735

[52] U.S. Cl 241/263, 83/411 A, 83/694, 83/697, 241/283 [51] Int. Cl. B02c l/00, B26d 1/10 [58] Field of Search 241/262, 270, 271, 263, 241/283; 83/411 A, 440, 444, 580, 694, 697;

[56] References Cited UNITED STATES PATENTS Berg 83/444 Lindars 91/275 3,021,035 2/1962 Hill 241/283 FOREIGN PATENTS OR APPLICATIONS 1,087,882 8/1960 Germany 241/263 Primary ExaminerRoy Lake Assistant Examiner-Craig R. Feinberg Attorney, Agent, or Firm-R. S. Sciascia; Roy Miller; Robert F. Beers [57] ABSTRACT A bone mill for converting cadaver bone into controlled size fragments. Bone is fed into a vertical channel which is horizontally intersected by a toothed cutter bar. The cutter bar shearingly contacts the front edge of the bone supply channel shearing the bone into fragments. The cutter bar is driven by an aircylinder driven by an external source of compressed air. A relay box on the bone mill may be unplugged from the mill and removed allowing the remainder of the mill to be sterilized in an autoclave.

2 Claims, 5 Drawing Figures PATENTEB UEC24 I974 sum 2 pg 3 BONE MILL BACKGROUND OF THE INVENTION 1. Field of the Invention.

This invention relates to devices for producing bone fragments which are employed to surgically repair diseased and damaged bone.

2. Description of the Prior Art.

Bone has been previously crushed manually by a commercially available hand operated mill. This, however, required a great deal of energy on the part of two individuals required to operate it. This limited the amount of bone that could be processed due to physical exhaustion of the operators of the machine. The present invention also, by providing a uniform and even stroke of the cutter bar, produces bone fragments of a more controlled size as compared to the various sizes of bone fragments produced by a manually operated bone mill.

SUMMARY OF THE INVENTION The invention comprises a bone mill for converting cadaver bone into fragments. Switches on the mill are hermetically sealed and other parts of the mill such as an air piston, bone feed shaft, cutter bar, and valves are of such nature that the entire mill, with the exception of a relay box which may be unplugged from the mill, may be sterilized in a hospital autoclave.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevational view of the invention;

FIG. 2 is an electrical diagram of the electrical controls of the invention;

FIG. 3 is a cross section taken in the direction of arrows lll III of FIG. 1;

FIG. 4 is a top view of the cutter bar; and

FIG. 5 is a side view of the cutter bar taken in the direction of arrows V V of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT The various parts of the invention are supported by a stainless steel base having a layer 12 of silicone rubber bonded to its bottom. The rubber increases friction preventing slippage and serves as a cushion while the invention is in operation. A cadaver bone that is to be milled is placed in bone supply channel 14 and is urged downwardly be weighted feed rod 16. Shear bar 18 runs perpendicularly to channel 14 and is guided by shear channel 20. All of these parts are supported and spaced apart from base 10 by supports 22. Forming the lower forward portion of bone supply channel 14 is shear piece 24 with shear edge 26 which interacts with teeth 28 of shear bar 18. Shear piece 24 is made of D-2 tool steel and shear bar 18 is made of 17-4 PH stainless steel.

Shear bar 18 is driven by modified Milwaukee Air Cylinder and Valve Combination (GV Series) 30. Air cylinder 30 is stainless steel with a baked on Teflon coating on the inner cylinder wall. The air cylinder thereby operates without a lubricant. Piston shaft 32 of air cylinder 30 is connected to shear bar 18 by linear alignment coupler 34. An external source of compressed air is supplied to air cylinder 30 through air hose 36.

Bar magnet 38 located on the bottom of linear alignment coupler 34 is encapsulated in epoxy and held on by heat shrinkable tubing 40. As magnet 38 moves back and forth over Teflon switch box 42 a pair .of hermetically sealed magnetic reed switches 44 are alternatingly actuated. Reed switches 44 are sealed in glass and potted in silicone rubber 46.

Reed switches 44 are electrically connected to relay box 48 by plugs 50. Relay box 48 in turn transfers a more powerful electrical signal via plug 52 to solenoids 58 located in Milwaukee Air Cylinder and Valve Combination 30 causing the piston shaft 32 to reciprocate in a well known manner. A ll0-volt electrical source is supplied to air cylinder 30 via line 54. When a source of compressed air is fed into the air cylinder, the shearing operation can be initiated by turning on switch 56 located on relay box 48.

The configuration of teeth 28 as shown in FIGS. 4 and 5 is a stairstep configuration. Also, the face of the teeth are slanted at from top to bottom as shown in FIG. 5.

When it is necessary to sterilize the invention in an autoclave, relay box 48 may be unplugged from the invention. The remainder of the mill can be sterilized in an autoclave without damage of its parts. Most of the parts of the mill are of stainless steel, Teflon or similar corrosive resistant material. When the mill is in use relay box 48 can be placed in a part of the room isolated from the rest of the mill.

What is claimed is:

l. A bone mill for converting cadaver bone into controlled size fragments comprising:

a bone supply channel;

a weighted feed rod located within said channel for pressing against a cadaver bone;

said rod fitting closely within said channel;

a shear channel perpendicularly intersecting said bone supply channel to form an aperture of constant cross section extending through the opposite walls of said bone supply channel;

a serrated shear bar having a set of teeth of stair-step configuration slidably movable within said shear channel and through said aperture;

means for reciprocating said bar to move completely across said bone supply channel for causing the interaction of said teeth and the bottom edge of said supply channel against a bone to shear the bone into controlled size fragments;

said reciprocating means comprising an air cylinder including a two-way piston shaft;

a pair of magnetic reed switches;

a linear alignment coupler connecting said piston shaft and said bar;

a magnet attached to said coupler for alternatingly actuating said reed switches;

said reed switches being parallel to and adjacent the movement of said magnet;

a valve on either side of said piston shaft for introducing compressed air into said cylinder; and

a solenoid associated with each said valve for opening and closing said valves in response to an electrical signal from said reed switches.

2. The device of claim 1 wherein:

said bar is rectangular cross sectional area having a major dimension substantially greater than the minor dimension; and the face of said teeth form an 85 angle with said major dimension. 

1. A bone mill for converting cadaver bone into controlled size fragments comprising: a bone supply channel; a weighted feed rod located within said channel for pressing against a cadaver bone; said rod fitting closely within said channel; a shear channel perpendicularly intersecting said bone supply channel to form an aperture of constant cross section extending through the opposite walls of said bone supply channel; a serrated shear bar having a set of teeth of stair-step configuration slidably movable within said shear channel and through said aperture; means for reciprocating said bar to move completely across said bone supply channel for causing the interaction of said teeth and the bottom edge of said supply channel against a bone to shear the bone into controlled size fragments; said reciprocating means comprising an air cylinder including a two-way piston shaft; a pair of magnetic reed switches; a linear alignment coupler connecting said piston shaft and said bar; a magnet attached to said coupler for alternatingly actuating said reed switches; said reed switches being parallel to and adjacent the movement of said magnet; a valve on either side of said piston shaft for introducing compressed air into said cylinder; and a solenoid associated with each said valve for opening and closing said valves in response to an electrical signal from said reed switches.
 2. The device of claim 1 wherein: said bar is rectangular cross sectional area having a major dimension substantially greater than the minor dimension; and the face of said teeth form an 85* angle with said major dimension. 